glibc/sysdeps/unix/sysv/linux/renameat.c

/* Copyright (C) 2005 Free Software Foundation, Inc.
   This file is part of the GNU C Library.

   The GNU C Library is free software; you can redistribute it and/or
   modify it under the terms of the GNU Lesser General Public
   License as published by the Free Software Foundation; either
   version 2.1 of the License, or (at your option) any later version.

   The GNU C Library is distributed in the hope that it will be useful,
   but WITHOUT ANY WARRANTY; without even the implied warranty of
   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
   Lesser General Public License for more details.

   You should have received a copy of the GNU Lesser General Public
   License along with the GNU C Library; if not, write to the Free
   Software Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA
   02111-1307 USA.  */

#include <errno.h>
#include <fcntl.h>
#include <stdio.h>
#include <sysdep.h>


/* Rename the file OLD relative to OLDFD to NEW relative to NEWFD.  */
int
renameat (oldfd, old, newfd, new)
     int oldfd;
     const char *old;
     int newfd;
     const char *new;
{
  static const char procfd[] = "/proc/self/fd/%d/%s";
  char *bufold = NULL;

  if (oldfd != AT_FDCWD && old[0] != '/')
    {
      size_t filelen = strlen (old);
      /* Buffer for the path name we are going to use.  It consists of
	 - the string /proc/self/fd/
	 - the file descriptor number
	 - the file name provided.
	 The final NUL is included in the sizeof.   A bit of overhead
	 due to the format elements compensates for possible negative
	 numbers.  */
      size_t buflen = sizeof (procfd) + sizeof (int) * 3 + filelen;
      bufold = alloca (buflen);

      __snprintf (bufold, buflen, procfd, oldfd, old);
      old = bufold;
    }

  char *bufnew = NULL;

  if (newfd != AT_FDCWD && new[0] != '/')
    {
      size_t filelen = strlen (new);
      /* Buffer for the path name we are going to use.  It consists of
	 - the string /proc/self/fd/
	 - the file descriptor number
	 - the file name provided.
	 The final NUL is included in the sizeof.   A bit of overhead
	 due to the format elements compensates for possible negative
	 numbers.  */
      size_t buflen = sizeof (procfd) + sizeof (int) * 3 + filelen;
      bufnew = alloca (buflen);

      __snprintf (bufnew, buflen, procfd, newfd, new);
      new = bufnew;
    }

  INTERNAL_SYSCALL_DECL (err);

  int result = INTERNAL_SYSCALL (rename, err, 2, old,  new);

  if (__builtin_expect (INTERNAL_SYSCALL_ERROR_P (result, err), 0))
    {
      int errval = INTERNAL_SYSCALL_ERRNO (result, err);
      if (errval == ENOTDIR && (bufnew != NULL || bufold != NULL))
	{
	  /* This can mean either the file descriptor is invalid or
	     /proc is not mounted.  */
	  struct stat64 st;

	  if (bufnew != NULL)
	    {
	      if (__fxstat64 (_STAT_VER, newfd, &st) != 0)
		/* errno is already set correctly.  */
		return -1;

	      /* If /proc is not mounted there is nothing we can do.  */
	      if (S_ISDIR (st.st_mode)
		  && (__xstat64 (_STAT_VER, "/proc/self/fd", &st) != 0
		      || !S_ISDIR (st.st_mode)))
		{
		  errval = ENOSYS;
		  goto out;
		}
	    }

	  if (bufold != NULL)
	    {
	      if (__fxstat64 (_STAT_VER, oldfd, &st) != 0)
		/* errno is already set correctly.  */
		return -1;

	      /* If /proc is not mounted there is nothing we can do.  */
	      if (S_ISDIR (st.st_mode)
		  && (__xstat64 (_STAT_VER, "/proc/self/fd", &st) != 0
		      || !S_ISDIR (st.st_mode)))
		errval = ENOSYS;
	    }
	}

    out:
      __set_errno (errval);
      result = -1;
    }

  return result;
}